Speaking of Hubble...

Archive: February 2012

At the Top

February 28, 2012 by Mario Livio
Hubble featured at the Carnival Parade 2012 in Sao Paulo, Brazil IMAGE CREDIT: Monica M. Marcon-Uchida

Hubble featured at the Carnival Parade 2012, Sao Paulo, Brazil IMAGE CREDIT: Monica-Midori Marcon-Uchida Sguazzard

A few events in the last few weeks should have convinced even the most extreme skeptics that the Hubble Space Telescope and the amazing images it has produced have become permanent icons within human culture.

First, National Geographic magazine published a special issue, entitled: “100 Scientific Discoveries that Changed the World.” Among those world-changing discoveries, at #78, you can find the Hubble Space Telescope!

The telescope is even mentioned in relation to two other earth-shaking topics: the inflationary universe, and extrasolar planets.

OK, you may think, clearly the telescope represents an impressive scientific achievement, but what about other arenas of “human culture”?

Well, Artforum is one of the leading international magazines on art. In its February 2012 issue, it features an article entitled “Top Ten” by sculptor and artist Maya Lin. Lin is perhaps best-known for designing the Vietnam Veterans Memorial in Washington, DC. In 1994, she was also the subject of the Academy Award-winning documentary “Maya Lin: A Strong Clear Vision.”

In her article, Lin lists the Top Ten subjects that she finds inspiring. Believe it or not, at #7, is “Images from the Hubble Space Telescope!”

Lin writes: “When I first saw NASA’s renderings of distant nebulae, I realized that these weren’t just reference photographs but, rather, works of art—and undoubtedly among the most powerful that our generation has produced.”

Finally, there is the realm of popular culture. There, HST was recently featured on a carnival float in Sao Paulo, Brazil!

I rest my case.

100 Billion Planets?

February 20, 2012 by Frank Summers
According to a statistical study, the Milky Way contains a minimum of 100 billion planets.

According to a statistical study, the Milky Way contains a minimum of 100 billion planets.

On Jan. 11, 2012, one of our Hubble news releases trumpeted that our Milky Way Galaxy “Contains at Least 100 Billion Planets.” Since astronomers have detected less than 2,000 planets around other stars, that may seem like a huge extrapolation of the data. It would mean another 50 million planets for every one we have detected.

But wait, the math gets even more astonishing. Reading the full story, one finds that the conclusion is based upon a survey that examined only 40 stars. And in only three of those observations were planets detected. Can astronomers really go from three detections to the conclusion of 100 billion planets? Let’s examine the reasoning.

First, recognize that most of the planets detected so far are large planets (like Jupiter) and relatively close to their stars. The main planet-detection techniques are less sensitive for smaller and more distant planets. The survey that brought about this news release used a different technique, gravitational microlensing, which notes the change in brightness that occurs when a star and its orbiting planet pass in front of another star, distorting its light with their combined gravity.

Gravitational microlensing can better detect a variety of planet sizes, although the number of detections is very small. In addition, unlike other techniques that concentrate on specific types of stars, microlensing surveys the full range of stars and thus produces more general statistics.

As noted above, 40 microlensing events were analyzed for planets and three planets were detected. It is likely that many more planets existed in these systems, but were not detected. Each event was observed many times, but the signatures of planets are short-lived and could have occurred during the gaps in the data. Also, the geometry of a star-planet system could lead to a planet signal too weak or too short to be detected.

The estimation of this “detection efficiency” is a complex statistical analysis to quantify the ideas expressed in words above. Note that the analysis relied on previous results, increasing the total number of planet detections from three to 10. One has to consider a range of planet sizes, a range of orbit diameters, and a range of orbit inclinations. How many planets would there have to be in total, in order for the observations to find the detected number?

The results indicate that about 17% of the stars should have a Jupiter-sized planet, 52% should have a Neptune-sized planet, and 62% should have a “super-Earth” planet (a planet about 5-10 times the mass of Earth). Those percentages, as input to the statistical model, yield the observed number of planets from the survey.

The full conclusion comes when generalizing to all the stars of the Milky Way. The results indicate that, on average, each star has at least one planet. With about a hundred billion stars in our galaxy, that means at least 100 billion planets.

Finally, the question must be asked as to whether these results are robust. What is the level of uncertainty? The statistical analysis measures these uncertainties and, even being pessimistic, the survey results indicate at least 50 billion planets. On the other end of the spectrum, the statistics could justify as many as 200 billion planets. No matter where in this range the true number may lie, the result is both intriguing and exciting.

Billions and billions of planets — that’s a lot of places to explore.

Astronomers Getting with the Times

February 13, 2012 by Jason Kalirai

AAS logo with TwitterI’ve attended the American Astronomical Society (AAS) general winter meeting since I started graduate school in 2001. At these meetings, upwards of 3,000 astronomers gather to present and hear new science results, form collaborations, organize smaller meetings with existing collaborators, and generally interact with one another. (For more information on what happens at an AAS meeting, see my blog entry from February 2011.) This year I went to the meeting with a new tool, Twitter.

Scientific discoveries are announced at the AAS meeting at a ferocious rate. Many news organizations are on hand, and they quickly write stories and issue press releases that describe our new understandings of the universe. Still, with a half-dozen parallel science sessions going on at once in different conference rooms, I always feel that I’m missing a lot of the action at the meeting.

A few months ago, I signed up for a Twitter account under the name @JasonKalirai. I’ve been using the social media service a few times every week to send out interesting tweets on astronomy pictures (e.g., Astronomy Picture of the Day) as well as other tidbits of information related to the Hubble and James Webb Space Telescopes. Occasionally, I share something personal, but usually it’s focused on astronomy. I keep up with what is being said in the “Twitterverse” much more than I tweet, and have found that I can stay on top of interesting developments in the scientific world as they happen.

At this year’s AAS meeting in Austin, Texas, I was happy to see astronomers and bloggers consistently use the #AAS219 hash tag on Twitter when discussing science results and events at the meeting. By simply following the hash tag, I could guarantee that I wouldn’t miss any of the big news. For example, I was in the poster room when I saw Twitter light up with an announcement of the discovery of the most distant cluster of galaxies by Hubble, and also of Kepler’s new discovery of the smallest exoplanets.

I found myself using the #AAS219 hash tag frequently in my own tweets during the meeting. I used this to announce several Webb initiatives and events that my group organized in Austin. For example, we put together a short community survey where astronomers could tell us which user tools they would find most beneficial. We also tweeted about our new Webb science brochures, the Hubble imagery being shown on the 3D TV at our booth, and various events.

When the power cut out during Nobel Laureate John Mather’s presentation on the Webb Space Telescope, I was able to tweet the link to slides I’d put together for him to use in his talk, allowing the audience to follow the images as he went into “freestyle mode.”

All together, over 4,000 tweets were sent using the #AAS219 hash tag. I found Twitter to be an extremely useful tool to share astronomy highlights, and will continue using it in the near future. I hope more astronomers will also jump on board, and begin using Twitter to exchange results from all meetings, domestic or international. At the same time, Twitter provides us with a powerful “public outreach” arena to inform the general population on the fascinating research that we do.

Now, time to tweet this article out.